OK sign

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1. MOJ Orthopedics & Rheumatology
Physical Examination: Extended OK Sign
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Abbreviations: LOAF: Lumbricals, Opponens Pollicis, Abductor
Pollicis Brevis, and Flexor Pollicis Brevis; EOK: Extended OK;
MCPJ: Metacarpophalangeal Joint; PIPJ: Proximal Interphalangeal
Joint; DIPJ: Distal Interphalangeal Joint
Introduction
A neurological examination of the upper limb can be grossly
assessed through hand examination. Orthopaedic examination
techniques illicit signs which inform the clinician about the
integrity of motor and sensory nerves, as well as musculoskeletal
function.
In general, the advent of investigations has greatly challenged
the perceived need for physical examinations [1]. However,
modern thought is that history taking, physical examinations and
investigations now form one sequential diagnostic entity, where
one informs the other [1,2]. A study by Peterson et al. [3], echoed
by Roshan [4], quantified the relative utility of each component
of diagnosing and found that, in 76% of patients, history led the
doctor to the correct diagnosis and that physical examination
and investigations then served to increase confidence in that
diagnosis [3,4].
History taking guides physical examinations which in turn
determines which investigations would best aid in further analysis
of the patient’s presentation [5]. Using physical examination also
prevents waste of needless investigations [5].
Due to the nature of orthopaedics it is possible to readily
illicit signs from the musculoskeletal system, and therefore
physical examination skills are essential. Neurological upper limb
examination reproducibility were determined to be moderate
to excellent, and therefore demonstrated important diagnostic
benefits [6].
Therefore, although investigations may appear to overshadow
physical examinations, in reality their utility remains essential in
diagnostic practice. Therefore progress and the development of
new and improved techniques should be encouraged and pursued.
Anatomy Review
The hand is defined as the portion of the upper limb distal to
the radiocarpal joint, and is composed of 27 bones, 14 of which
are phalanges, 5 metacarpal bones, and 8 carpal bones.
Intrinsic and extrinsic muscles of the hand are responsible
for the wide range of broad and intricate movements. The
extrinsic muscles originate from the forearm whilst the intrinsic
muscles originate and terminate within the compartment of the
hand. Intrinsic muscles of the hand include: thenar, hypothenar,
interosseous muscles (four dorsal, and three volar), and the
lumbricals. The thenar eminence is found on the radial side of
the palm, and is made up of three muscles: The abductor pollicis
brevis superficially, which causes thumb abduction, flexor pollicis
brevis which causes thumb flexion, and opponens pollicis which
is deep to the abductor pollicis longus and facilitates opposition
of the thumb. The hypothenar eminence lies on the ulna side of
the palm and is made up of three muscles: Abductor digiti minimi,
flexor digiti minimi which causes flexion of the fifth digit, and
opponens digiti minimi. Palmaris brevis is sometimes considered
to be part of the hypothenar, however it is so thin it cannot be
distinguished from the three hypothenar muscles deep.
All hand muscles are innervated by three main nerves: Radial,
ulna, and median. These branch out from the brachial plexus,
which extends from the C5 to T1 spinal nerves.

Volume 9 Issue 2 - 2017
1
Arthroplasty Fellow, Department of Trauma and Orthopaedic,
Royal Liverpool University Hospital, UK
2
Senior House Officer, Department of Trauma and
Orthopaedic, Royal Liverpool University Hospital, UK
3
Orthopaedic Consultant, Department of Trauma and
Orthopaedic, Warrington and Halton Hospitals NHS
Foundation Trust, UK
*Corresponding author: Fabienne Marie-Louise Robertson,
BA, MBBS, MPH, Senior House Officer, Department of Trauma
and Orthopaedic, Royal Liverpool University Hospital,
Prescot St, Liverpool, L69 3GA, UK, Email:
Received: July 26, 2017 | Published: October 20, 2017
Research Article
MOJ Orthop Rheumatol 2017, 9(2): 00353
Abstract
This article presents an elaboration of the widely used neurological examination
OK sign, which by itself tests the anterior interosseous motor branch of the median
nerve. However, the OK sign has the potential to be incorporated into an examination
technique which tests several nerves simultaneously. The OK sign would continue
to test the anterior interosseous nerve, whilst a simultaneous wrist extension
additionally tests the radial nerve, metacarpophalangeal joint extension tests the
posterior interosseous nerve, and abduction of the third to fifth digits tests the ulna
nerve. This ensemble of manoeuvers has the ability to succinctly test the majority of
motor nerves of the hand in a single smooth set of movements. As this multi-motor
neurological test is a progression of the OK sign, the development has been called the
‘Extended OK’ sign; EOK.
Keywords: Physical examination; OK sign; Extended OK sign; EOK; Medial nerve;
Radial nerve; Ulna nerve; Motor innervation; Hand

2. Citation: Mohammed AA, Robertson FML, Shah N (2017) Physical Examination: Extended OK Sign. MOJ Orthop Rheumatol 9(2): 00353.
DOI: 10.15406/mojor.2017.09.00353Physical Examination: Extended OK Sign
2/3Copyright:
?2017 Mohammed et al.
The radial nerve innervates the posterior compartment of the
arm, namely the medial and lateral heads of the triceps brachii,
and the posterior osteofascial compartment of the forearm,
including brachioradialis, aconeus, extensor carpi radialis longus.
It then divides into deep and superficial branches, where the
former becomes the posterior interosseous nerve, whilst the
latter provides sensory information to the dorsum of the hand.
The deep branch becomes the posterior interosseous nerve after
the supinator and innervates the extensor muscles of the hand
and wrist as well as abductor pollicis longus.
The median nerve enters the upper limb from the axilla past
the inferior border of teres minor, then descends along with the
brachial artery, starting laterally then crossing anteriorly to lie
medial to the artery, on the medial side of the arm between the
biceps brachii and brachialis. The nerve then passes anteriorly
over the medial epicondyle into the cubital fossa medially, then
continues into the forearm between the two heads of pronator
teres, then between c, and finally emerges between the flexor
digitorum superficialis and flexor pollicis longus. Starting
proximally the median nerve innervates pronator teres, flexor
carpi radialis, palmaris longus, and flexor digitorum superficialis.
Just distal to the lateral epicondyle, the median nerve gives off
the anterior interosseous nerve which innervates flexor pollicis
longus, flexor digitorum profundus for the lateral second and
third digits, and pronator quadratus. Finally, the medial nerve
passes through the carpal tunnel on the volar aspect of the wrist,
deep to the flexor retinaculum, and then divides into motor
and sensory branches: The recurrent branch provides motor
innervation to the muscles of the thenar compartment, and the
digital cutaneous nerve divides into the common and proper
palmar digital branches which provide sensation to lateral palmar
aspect of the hand and the dorsum of the fingertips of the first to
third digits including the lateral aspect of the fourth digit. Finally
the recurrent nerve is responsible for the motor innervation of
the thenar muscles (Opponens pollicis, Abductor pollicis brevis
and Flexor pollicis brevis) and the first and second Lumbricals
which flex the metacarpophalangeal joint and extends the
interphalangeal joints. All four of these muscles innervated by the
recurrent nerve are known as the LOAF muscles.
The ulnar nerve is derived from the C8 to T1 nerves of the
brachial plexus. The nerve then descends posteromedially down
the humerus and passes behind the medial epicondyle (cubital
tunnel) after which it enters the anterior compartment of the
forearm. As the nerve descends, alongside and inferior to the
ulnar artery, it supplies flexor carpi ulnaris and the medial half
of flexor digitorum profundus for the 4
th
and 5
th
digits. Before
entering the palm of the hand, through the ulnar canal (Guyon’s
canal), the nerve divides into three branches: Muscular, palmar
and dorsal branches of the ulnar nerve. Once the ulna nerve passes
over the superficial retinaculum it gives off two branches, namely
the superficial and deep branches of the ulnar nerve, where the
former innervates palmaris brevis and provides sensation over
the palmar aspect of the third and fourth digits, and the latter
innervates adductor pollicis longus, third and fourth lumbricals,
interosseous muscles, and the hypothenar muscles (flexor digiti
minimi, abductor minimi and opponens digiti minimi).
To summarise, the motor functions of the hand are controlled by
three main nerves: The radial nerve causes extension of the wrist
and digits. Whilst the median nerve is responsible for abduction
and flexion of the thumb, opposition, and first and second digit
metacarpophalangeal flexion and interphalangeal flexion and
extension, and third and fourth proximal interphalangeal joint
flexion. Finally, the ulnar nerve is associated with thumb adduction
and flexion, third and fourth metacarpophalangeal flexion and
interphalangeal joint extension, and adduction and abduction of
first to fourth digits.
The Extended OK Sign
A common test used in clinical practice is the OK sign which
grossly verifies the integrity of the median nerve, and specifically
tests the anterior interosseous nerve. In this study we propose an
Extended OK (EOK) sign which builds upon the traditional OK sign,
and subsequently involves the following: OK sign (flexed index,
flexed thumb), extended wrist, extended metacarpophalangeal
joints (MCPJ), extended proximal interphalangeal joint (PIPJ),
extended distal interphalangeal joint (DIPJ) of the 3
rd
, 4
th
and 5
th

digits, and abducted 3
rd
, 4
th
and 5
th
digits (Figure 1).
As previously mentioned, motor innervation of hand muscles
is supplied by the radial, ulna, median nerves. In addition to the
initial OK sign, which tests the anterior interosseous branch of the
median nerve, wrist extension then tests the integrity of the radial
nerve, digit extension reflects the integrity of the radial nerve and
extensors, whilst metacarpophalangeal extension reflects the
posterior interosseous nerve function, and digit abduction reveals
the function of the ulnar nerve.
The suggested order of examination is as follows:
a. OK sign (1
st
and 2
nd
digit flexion)
b. Wrist extension
c. Digit extension (3
rd
4
th
5
th
MCPJ, PIPJ, DIPJ)
d. Digit abduction (3
rd
4
th
5
th
digits).
With the Extended OK sign, in one composite set of movements,
upper limb motor nerve function is primarily tested.
Figures 1: Physical Examination: Extended OK Sign-OK Sign, Extension
Wrist and 3
rd
-5
th
Digits, Abduction of 3
rd
-5
th
Digits – Dorsal and Lateral
Views.

3. Citation: Mohammed AA, Robertson FML, Shah N (2017) Physical Examination: Extended OK Sign. MOJ Orthop Rheumatol 9(2): 00353.
DOI: 10.15406/mojor.2017.09.00353Physical Examination: Extended OK Sign
3/3Copyright:
?2017 Mohammed et al.
Discussion
Specifically, extension of the wrist and digits tests the majority
of the extensor tendons though does not specifically test the
abductor pollicis longus. Therefore the integrity of the radial
nerve is tested up to the level of the wrist and then more distally
with the digits, but not medial innervation to the thumb. An extra
examination for abductor pollicis longus would be needed to
completely test the radial nerve.
The OK sign specifically tests for the anterior interosseous
nerve which means it does not completely test for flexor digitorum
superficialis, flexor digitorum profundus nor the LOAF muscles.
More specific tests would be needed to complete examination
of the median nerve for flexor digitorum superficialis, flexor
digitorum profundus as well as the recurrent motor branch for
the LOAF muscles.
Abduction of the digits is innervated by the deep ulna nerve
which is a continuation of the ulna nerve. However, the function of
the hypothenar muscles, medial lumbricals and adductor pollicis
are not specifically tested and so further tests for the branches of
the ulna nerve within the hand would need to be carried out to
complete the examination of the motor ulna nerve.
The EOK examination is a screening tool and does not have the
pretense of testing every digital branch of all three nerves and is
not meant to provide a complete neurological assessment. Rather
it has the ability to succinctly illicit potential motor deficits which
will then require further examination and investigation.
General tests are taught to screen for possible hand injuries:
Extension of the wrist and digits is taught to test the radial nerve,
digit abduction as an indicator of ulna nerve function, and an
intact OK sign demonstrates integrity of the median nerve. This
EOK sign combines these basic principles into one succinct test,
which in one move is able to generally test the motor innervation
of the hand and reveal whether there exists a motor neurological
deficit requiring further evaluation.
At a time when clinicians are increasingly specialized and the
role of non-doctor staff is developing, there is a need to establish
sensitive tests which allow non-hand surgeons to screen patients
for hand pathologies. Indeed, hand injuries are very common
though the education and knowledge required to correctly
diagnose hand pathologies is mostly restricted to orthopaedic and
plastic surgeons. In view of this, proposing user-friendly physical
examination tests which can illicit potential hand pathologies
would address this gap of expertise and allow clinicians to screen
for hand injuries in an efficient and straight forward manner.
These latter characteristics of the examination, make the EOK sign
also suitable for screening in trauma scenarios, multiple injury
cases, and as an initial assessment of hand motor innervation. If
an issue is identified by the EOK sign then further specific tests
would be warranted.
Conclusion
The Extended OK sign is a straight forward evolution of the
traditional OK sign offering an effective and efficient neurological
screening test for the motor nerves of the hand. This test is
sensitive for the majority of the three main hand motor nerves
and would be useful in areas where time and/or expertise are
limited.
At a time where investigations are the focus of innovation, it
is important to highlight the continued significance and necessity
to develop physical examination as an essential diagnostic tool in
patient management. The Extended OK sign is a quick screening
test for the radial, median, and ulna nerves which can be easily
applied and taught.
I put it forward that, by adding three sequential movements
to the widely used OK sign, namely wrist extension then
metacarpophalangeal joint extension, followed by digit extension
then abduction, the Extended OK sign is a logical clinical
progression which has the ability to provide a quick and relatively
simple general motor innervation screening test of the hand.
Acknowledgement
None to declare.
Statement of Funding
This article received no specific grant from any funding agency
in the public, commercial, or not-for-profit sectors.
Conflict of Interest
The authors declare that they have no conflict of interest.
Statement of Human and Animal Ethics
This article does not contain any studies with human or animal
subjects.
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